How To Disassemble The Window/burner Unit To Replace The Thermocouple?

Getting that inner door assembly off for me required disconnection of the Burner from the inner door - otherwise I couldn't get the burner to wiggle out of the burner access door. I've attached a quick annotated image. After removing the 4 Burner Hex Nuts, the access door assembly should come free and you can separately pull out the burner.

Looking at this after the fact, I think it may have been the burner getting caught on the Insulation around the access door - it would be worth checking whether you can get it out without removing the burner: carefully pushing the insulation back into the walls might give you enough space to pull it out, but I wouldn't recommend forcing it.

Rheem (who manufactures these) has a Pilot Light assembly kit that you can pick up from Rheem directly or on Amazon or Home Depot under the part number SP20790 that includes the Pilot Assembly (Thermocouple, Pilot tube and Piezoelectric starter wire) as well as gaskets, brackets, clips, nuts and screws. The inner door gasket is supposed to be replaced if the inner door is removed, which I needed to do to disconnect the burner. The Rubber gasket through which the tubes pass disintegrated as I disassembled, so this kit was a must for me. At the Time of writing, Rheem sells it directly for $65, but also available at HomeDepot.com for $44. If you want to go whole hog, the full burner assembly is available too under the PN: SP20150

If you need parts for this in the future, hit parts.rheem.com, type in your unit's SN and it will pull them up along with the use and care manual (attached).